Industry-Science-Medical (ISM) bands such as 2.4 GHz band are used by various types of industrial equipment. The industrial equipment generates electromagnetic waves that may interfere with wireless communication of communication devices for wireless communication. Some of the interference sources are electromagnetic waves having a periodicity. There is a possible method that detects the periodicity of the electromagnetic waves and performs wireless communication based on the detection result in order to avoid influence of the interference.
An exemplary interference source having the periodicity includes an unnecessary electromagnetic wave that is radiated from a microwave oven in a wide band in the 2.4 GHz band. Another exemplary interference source having the periodicity includes a beacon signal from access points (AP) of a wireless local area network (LAN) compliant with Institute of Electrical and Electronics Engineers (IEEE) 802.11b standard and IEEE 802.11g standard.
Recently, a following wireless communication method has been proposed. In this method, a transmitting device side performs transmission on a certain channel in the band while a receiving device side performs reception on all the channels in the band without a narrow band filter that extracts a signal on one channel in the band. This method can save the cost of the receiving device side.
Even in the case where the transmitting side performs transmission on the one channel while the receiving side performs reception on all the channels, the transmitting side can perform transmission on the one channel without being affected by the interference. However, a problem arises in that the receiving side is interfered by the electromagnetic wave that is radiated from another interference source.